ocp-fix-errors: recover version before Tiphaine's changes
ocp-ppx: add an interface to ppxPlugin
ocplib-system: in File, add a sub-module for raw IOs

File.RawIO implements primitives using strings instead of File.t
They should be used by other functions of File.t

TODO: we should rewrite this module completely, in particular we should
probably cut it in two modules, one depending only on Pervasives, the
other one of Unix only.
Merge branch 'typerex2' of github.com:OCamlPro/typerex into typerex2

Conflicts:
	tools/ocp-build/buildEngine.ml